The following enzymes involved in the metabolism of the prostaglandins will be measured in tissues and in body fluids: 15- hydroxy-PGF 2 alpha dehydrogenase, 15-keto-PGF 2 alpha (delta 13.14) reductase, 13,14-dihydro-PG-15-keto reductase, PGE-9-keto reductase, PGE dehydrase, and PGA isomerase. The prostaglandin synthetase system will also be measured in various tissues. All of these enzymes will be measured with antibodies directed specifically toward the substrate and/or the product of the appropriate enzymatic reaction. The various classes of prostaglandins and their metabolites will also be measured in tissues and in body fluids, for example, levels of prostaglandin- metabolites in amniotic fluids in normal and abnormal pregnancies. Many of the enzymes mentioned above will be purified and characterized. Serological means will be used to compare enzymes with a common function from different organs. We anticipate that quantitation and identification of the pharmacologically active prostaglandins, their metabolites, and the activities of the biosynthetic and metabolic enzymes will give some clues concerning the mechanisms by which prostaglandins act.